Control devices of injection molding machines, each including a molding machine controller having a computer function to perform molding by respectively controlling a mold clamping device that clamps (also opens and closes) a mold and an injection device that injects and charges resin, plasticized and molten by rotation of a screw inside a heating cylinder, into the mold by advancement of the screw, are conventionally known. According to such a control device, the molding is usually performed by controlling the mold clamping device to clamp the mold with a high-pressure clamping force, and controlling the injection device by preset molding conditions (an injection velocity, a screw position, a V-P (velocity-pressure) switchover point, a dwelling force and the like) to inject and charge the resin into the mold (refer to Patent Literature 1).
Meanwhile, there is a demand for energy saving of industrial machinery including the injection molding machine, from the viewpoint of global environmental protection such as reduction of carbon dioxide emissions, resource conservation and the like. The present inventor has already proposed an injection molding method capable of responding to the demand in Patent Literature 2. It is an object of this injection molding method to respond to the demand for the energy saving from the viewpoint of the global environmental protection such as the reduction of carbon dioxide emissions, the resource conservation and the like, by applying only a required amount of pressure to the mold when necessary. Specifically, at the time of performing injection molding by injecting and charging molten resin from the injection device into the mold having a fixed mold and a movable mold supported by a mold opening/closing device, a clearance (set interval) between the fixed mold and the movable mold is set in advance in which the molten resin does not enter at the time of injection molding. At the time of molding, the molten resin is injected and charged from the injection device into the mold that is closed while leaving the clearance of the set interval, and position control of the movable mold is performed so that the set interval is fixed at least during injection and charging.